1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer-readable storage medium for processing an intraluminal image that is a captured image of an intralumen.
2. Description of the Related Art
Conventionally, endoscopes are widely used as medical observation apparatuses inserted into a body of a subject such as a patient to observe the inside of an intralumen. In recent years, swallowable endoscopes (capsule endoscopes) provided with an imaging apparatus, a communication apparatus that transmits image data captured by the imaging apparatus wirelessly to the outside of a body, and the like in a capsule-shaped casing have been developed. Because observation and diagnosis of such an image of an intralumen (intraluminal image) captured by such medical observation apparatuses need a lot of experience, a medical diagnosis support function that assists diagnosis made by a doctor is required. As one of the image recognition technologies to realize the function, a technology in which an abnormal portion such as a lesion is detected automatically from an intraluminal image to be shown to a doctor, for example, has been developed.
For example, Japanese Laid-open Patent Publication No. 2002-099896 discloses a technology in which a shape-dependent filter is used to stably detect a candidate of a minute calcified shadow, which is one of the characteristics of a cancerous region in breast cancer, without being influenced by a rough structure and a linear structure. In Japanese Laid-open Patent Publication No. 2002-099896, based on an assumed shape of a minute calcified shadow, a second shape-dependent filter with filter characteristics optimized in accordance with imaging conditions, reading conditions, various conditions such as image contrast and the size of the minute calcified shadow, or a combination of these conditions is prepared in advance. Then, a linear structure in the image is eliminated using a first shape-dependent filter serving as a morphological filter (for example, refer to Kohata, et al., “Extraction of Microcalcifications Using Morphological Filter with Multiple Structuring Elements”, Transactions of the Institute of Electronics, Information, and Communication Engineers of Japan, D-II, Vol. J75-D-II, No. 7, pp. 1170-1176, July 1992, and Kohata, et al., “Fundamentals of Morphology and Its Application to Mammogram Processing”, Medical Imaging Technology, Vol. 12, No. 1, January 1994), whereby a minute structure image that indicates a minute structure portion is generated. Subsequently, by performing enhancement process on the minute structure image using the second shape-dependent filter thus prepared, an enhancement-processed image in which a minute calcified shadow candidate alone is enhanced relatively compared with the circumference (portions other than the minute calcified shadow candidate including rough structure portions and linear structure portions that cannot be eliminated by the first shape-dependent filter).